The present invention relates generally to petroleum resins suitable as tackifiers for adhesive formulations and methods for their production. More particularly, the present invention relates to a novel quenching procedure which results in a petroleum resin having improved color properties.
The present invention is primarily concerned with petroleum resins derived from aliphatic monomers, aromatic monomers and mixtures thereof. These petroleum resins are well-known in the art and are described in numerous patents and publications such as, for example. U.S. Pat. Nos. 4,391,961; 4,419,503; 4,514,554, 4,558,107; 4,562,233; 4,636,555; 4,684,707; and 4,714,749. All of these patents are incorporated by reference for all purposes as if fully set forth.
Petroleum resins are generally produced by polymerizing olefinic, diolefinic, aromatic and/or mixed feedstocks in the presence of a Friedel-Crafts catalyst, usually an aluminum chloride or boron triflouride, at temperatures of between about -40.degree. C. to about 100.degree. C. and pressures ranging from atmospheric up to about 100 psig.
As a key step in the above process, the resulting polymerizate is quenched to deactivate the active catalyst residue and convert the catalyst to a more easily removable form. Prior art quenching procedures involve the washing of the polymerizate with large volumes of water or combinations of water and an alcohol or alkali solution to deactivate and remove the catalyst from the polymerizate. Such quenching procedures are more fully taught in the aforementioned incorporated patents.
The water wash ("wet") quenching procedures, however, often result in dark colored products. Additionally, the large volumes of water utilized in the quench procedures, generally on the order of about 10% to about 200% of the polymerizate, results in substantial treatment and disposal problems.
The present invention overcomes these shortcomings by utilizing a "dry" quench procedure involving the addition of minor amounts of a phosphite to the petroleum resin polymerizate as more fully described below.